The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly to a semiconductor device which is capable of simultaneously improving the short channel effect of a PMOS and stabilizing the current of an NMOS and a method for manufacturing the same.
The gate material of a MOSFET device is mainly made of a polysilicon layer, because the polysilicon layer displays the physical properties required in a manufacturing process for a semiconductor device, such as a high melting point, ease of forming a thin film, ease of patterning a line, stability in an oxidation atmosphere and formation of a planarized surface. In an actual MOSFET device, a polysilicon gate contains a dopant such as phosphorous (P), arsenic (As) or boron (B), thereby ensuring low resistance.
Also, in a CMOS device, an NMOS and PMOS are all formed with an N+ polysilicon gate. In this case, the NMOS has a surface channel and the PMOS has a buried channel by a count doping.
Meanwhile, as the level of integration of semiconductor devices increases the width of the gate electrode has decreased. Unlike the NMOS having a surface channel, the PMOS is disadvantaged by an increase in short channel effect, such as the punch-through phenomenon, due to the buried channel.
Accordingly, there has been suggested a method in which an elevated source/drain area is formed on both sides of the polysilicon gate. The elevated source/drain area increases the effective channel length thereby improving the short channel effect of the PMOS.
However, in the prior art described above, it is difficult to increase the current since the elevated source/drain area is formed with a shallow depth within the semiconductor substrate. Therefore, the prior art is limited in its ability to ensure the stability of the current of the NMOS.
Also, because the NMOS has a larger variation in current as compared to the PMOS, it is important to ensure the stability of the current of the NMOS device in order to enhance the operational characteristics of the semiconductor device. No method, however, has been developed which is capable of simultaneously improving the short channel effect of the PMOS and ensuring the stability of the current of the NMOS. Therefore, it is necessary to find the solution.